The present invention is an improvement in automatic firearms of the recoil-operated type wherein the various operations of extracting, ejecting, loading and cocking are performed by the energy of the barrel and breech bolt recoiling in the receiver on firing, and particularly, recoil-operated firearms of the short-recoil type. In short-recoil operated automatic firearms, the breech bolt is locked to the barrel at the instant of firing and remains locked along a relatively short recoil path, after which the breech bolt is automatically unlocked from the barrel, the barrel stops recoiling, and the breech bolt continues its recoil, extracting and ejecting the spent cartridge case. The barrel may be returned immediately, by a return spring or recoil buffer, to its forward or battery position, or may be held in its recoil position, by a barrel lock, until the breech bolt returns.
The breech bolt may be held near its fully recoiled position by a trigger sear, and/or an automatic sear that is released by the cartridge feed mechanism. The trigger sear is held retracted by the trigger during fully automatic firing. When the breech bolt is released from both sears, it is moved forwardly by its drive spring and pushes or rams a cartridge, e.g., from a belt, into the barrel chamber. At or about the point where the breech bolt engages the barrel, it is automatically locked to the barrel and, if the barrel has not yet returned to battery, the barrel lock is automatically released and the locked breech bolt and barrel return to battery position. Firing may occur automatically at any desired time after breech bolt locking, preferably during the barrel return in order to minimize the recoil action on the firearm mount.
The conventional short-recoil operated firearm has at least two separate locks, namely, at least one bolt lock and a barrel lock, which are critically timed. The timing of these locks is affected by excessive lock wear, and may be magnified by bolt-barrel bounce. When the timing is affected, the weapon functioning becomes erratic and may cease to operate, thus necessitating replacement of the locks as well as possible replacement of the lock operating cams.
In accordance with the present invention, the various bolt and barrel locks in a short-recoil operated automatic firearm are replaced by a single locking member comprising means for alternating locking the breech bolt and the barrel. In the embodiment illustrated as an example, the unitary bolt-barrel lock member is a lever pivoted intermediate its ends on the barrel, near the rear end thereof, and comprising a forward arm engageable with an abutment of the receiver, e.g., the barrel buffer, a rear arm having a hook portion engageable with a lateral projection on the breech bolt, and an intermediate arm engageable by the breech bolt in its forward motion to release the barrel lock from the receiver. The lock member is spring-pressed toward its barrel-locking position.